Shielding for vertical break switches of high voltage rating



p 1970 H. ALBRIGHT 3,530,265

SHIELDING FOR VERTICAL BREAK SWITCHES OF HIGH VOLTAGE RATING Filed May 28, 1969 2 Sheets-Sheet 1 I EE-"L IN VENTOR. 0) flza/e/a/w v Sept. 22, 1970 ALBRlGHT v3,530,265

SHIELDINGFOR VERTICAL BREAK SWITCHES OF HIGH VOLTAGE RATING Filed May 28, 1969 2 Sheets-Sheet 2 I 43/, I /Z United States Patent 3,530,265 SHIELDING FOR VERTICAL BREAK SWITCHES OF HIGH VOLTAGE RATING Roy H. Albright, Greensburg, Pa., assignor to I-T-E Imperial Corporation, Philadelphia, Pa., a corporation of Delaware Filed May 28, 1969, Ser. No. 828,566 Int. Cl. H01h 31/00 US. Cl. 200-48 3 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to disconnect switches and more particularly to disconnect switches of the vertical reach type wherein there are provided metallic shield members for reducing dielectric stress concentration in the region of the free end of an energized blade which is in either the open or closed position.

Disconnect switches of extra high voltage (EHV) ratings require shielding of the live switch parts in order to reduce dielectric stress concentration, the occurrence of which could result in the production of objectionable corona discharge and/or radio interference. Eifective shielding is provided in conventional disconnect switches through the use of shield rings positioned on each side of the blade hinge mechanism and the jaw contacts which receive the free end of the switch blade. In addition thereto, the blade end must be fitted with a metallic sphere to reduce dielectric stresses in the region of the blade end when the switch is in the open position.

Normally, there is no problem of shielding in conventional vertical break switches in which the blade is closed when in a horizontal position and open when in a vertical position, However, the problem of shielding becomes more pronounced with the advent of vertical reach switches wherein the blade is closed when in the vertical position and open when in the horizontal position. The use of a sphere at the free end of the blade creates a problem in that it adds to the operating effort required to move the blade between open and closed positions and further interferes with ice (rain or sleet) shielding means (in applications where such protective means is required) located above the jaw contacts.

The present invention is characterized by means provided to create adequate corona shielding of an energized blade while at the same time eliminating the need for the metal sphere on the blade end of the switch.

The vertical reach switch of the present invention is comprised of a support for mounting the hinge and blade operating components a predetermined distance above ground. Suitable metallic shield means are positioned on opposite sides of the hinge and operating linkage assemblies to reduce dielectric stress concentration in this region. The hinge assembly supports the switch blade which extends outwardly and away from the hinge assembly and is aligned substantially horizontally when in the open position.

The operating assembly for the disconnect switch is designed to rotate the blade from the open (horizontal) ice position to the closed (vertical) position wherein the beaver-tail portion of the blade is arranged to move into and firmly be engaged by the jaw contacts of a disconnect switch jaw structure which is secured to an overhead wire or other support spaced above the hinge section by a predetermined distance. The jaw structure is provided with spring biased jaw members which are arranged to firmly embrace and electrically engage the beaver-tail portion of the blade as the blade is caused to pivot about its hinged end and rotate about its longitudinal axis such that the beaver-tail section twists into electrical engagement with the jaw structure.

The jaw structure is provided with a pair of metallic shield means positioned on opposite sides of the jaw structure to reduce dielectric stress concentration of the jaw structure when the disconnect switch is in the closed position and alternatively when the disconnect switch is in the open position and the overhead conductor secured to the jaw structure is energized.

A horizontally aligned cantilevered support is secured to the hinge and operating mechanism support and is provided with a pair of metallic shield members arranged to lie on opposite sides of the free end of the switch blade when in the open position. The shield members are provided to reduce dielectric stress concentration at the beaver-tail end of the switch blade in those applications wherein the blade, hinge and operating mechanism are energized and the blade is in the open (horizontal) position.

Since the blade is relatively rapidly moved between the open and closed positions no significant concern need be given to the disconnect switch structure in this transient state. However, since the blade may be maintained for indefinite periods of time in either the closed or the open position it is important that means for relieving the dielectric stress concentration be provided to protect the structure when in either of these two semi-permanent states.

Since the blade length of disconnect switches is quite appreciable (especially those utilized in extra high voltage applications wherein lengths of the order of 22 feet or more are encountered) a very substantial operating force must be provided to move the blade. It therefore becomes important to reduce the blade moment as much as is practically possible. Conventional corona shielding techniques generally employ metallic spheres at the end of the blade which increase the weight of the blade as well as its length. The use of metallic shields designed in accordance with the principles of the present invention have been found to decrease the blade moment by as much as 12% which reduction is reflected in a reduced operating effort. In addition thereto, in climatic environments wherein ice loading is significant and the blade and sphere are subject to ice loading thereby leading to further significant increases in blade moments, it has been found that the blade moment approaches an objectionable operating elfort requirement. Such ice loading upon the sphere also either prevents or interferes with the protection of the jaw structure against ice build-up causing connect switch experiences driving rains or sleet. By elimination of the sphere at the beaver-tail end of the blade, the ice protective shield can be positioned in closer proximity to the jaw so as to be more effective in preventing ice accumulation upon the jaw contact fingers.

It is therefore one object of the present invention to provide a novel structure for vertical reach disconnect switches and the like in which energized components of the structure are protected against dielectric stress concentration when maintained in either the open or closed positions.

Still another object of the present invention is to provide a novel shielding structure for vertical reach disconnect switches having extra high voltage ratings, said shielding means reducing the dielectric stress concentration in the region of the switch, jaw, hinge and blade end members while eliminating the need for a metallic sphere employed at the beaver-tail end of energized blades in conventional structures which arrangement results in a significant reduction in the operating forces required to move the blade between the open and closed positions.

Still another object of the present invention is to provide a novel shielding structure for vertical reach disconnect switches having extra high voltage ratings, said shielding means reducing the dielectric stress concentration in the region of the switch, jaw, hinge and blade end members while eliminating the need for a metallic sphere employed at the beaver-tail end of energized blades in conventional structures which arrangement results in a significant reduction in the operating forces required to move the blade between the open and closed positions and further enables closer positioning of a rain shield to the jaw structure thereby providing more effective protection against rain, sleet and/ or ice accumulation.

These as well as other objects of the present invention will become apparent when reading the accompanying description and drawings in which:

FIG. 1 shows a vertical reach disconnect switch utilizing the principles of the present invention.

FIG. 2 shows another alternative embodiment of the invention.

The disconnect switch 10 shown in the figures is comprised of a metallic supporting structure 11 which may be mounted upon the ground or any other suitable support and which, in turn, provides support for a pair of elongated insulators 12 and 13. The upper end of insulators 12 and 13 supports a blade hinge and operating mechanism 14 which pivotally mounts the left-hand end of an elongated blade 15 thereto. The hinge and blade operating mechanism 14 may be of the type described in US. Pats. No. 2,673,902 issued Mar. 30, 1954 and No. 2,854,553 issued Sept. 30, 1958, both of which patents have been assigned to the assignee of the present invention. As is conventional in the disconnect switch art, such apparatus is typically comprised of a movable switch blade which is first rotated about a pivot r hinge substantially at one end thereof so as to move into the region of its cooperating jaw contact. During a part of this rotational movement the operating mechanism is designed to simultaneously rotate the blade about its longitudinal axis so as to bring its beaver-tail contact portion into rigid engagement with the cooperating contact surfaces of the jaw which then provides good engagement under pressure between jaw contacts and beaver-tail contacts. The operating assembly is normally driven by one of the insulators, for example, insulator 13 which is pivotally mounted between support 11 and hinge and operating assembly 14. The lower end of the insulator is normally provided with an operating arm or crank coupled to a motor source for imparting either closing or opening movement to blade 15. The details of the driving source and operating mechanism have been omitted herein for purposes of simplicity, it being understood that such mechanisms are described in previously issued patents such as for example, the patents recited hereinabove.

A pair of metallic closed loop shield members 16'and 17 are positioned on opposite sides of the hinge and operating mechanism 14 to reduce the dielectric stress concentration of this assembly, which concentration is especially critical due to the sharp edges or other points provided along certain of the components of the operating mechanism. Such shields are typically referred to as corona shields. Both of the shield members are formed of a hollow tubular metal such as, for example, aluminum. Shield 16 is shown as being secured to assembly 14 by means of brackets 16a and 16b. It should be understood that similar brackets are provided for securing shield 17 to assembly 14, which brackets have been omitted for purposes of simplicity. Although the preferred embodiment shows closed-loop corona shields it should be understood the solid plate-like members or other metallic shapes and configurations may be employed so long as surface contours of the shields are sufficiently rounded to limit electrostatic stress concentration to an acceptable amount.

The solid line blade 15 is in the open position. The free end of the blade is provided with a beaver-tail section 15a which may, for example, be of the type described in detail in US. Pat. No. 3,388,225 issued June 11, 1968 to the assignee of the present invention.

The blade is moved from the solid line position 15 toward the dotted line position 15' by means of the operating mechanism referred to previously which pivots the blade assembly through an angle 0 from the horizontal position to the vertical position (15) and, during a portion of this pivotal movement rotates the blade about its longitudinal axis so as to twist the leaver-tail portion into firm engagement with the contacts of the jaw assembly 18. As is described in detail in the above mentioned U.S. Pat. 3,388,225 the widest dimension of the beaver-tail configuration is slightly greater than the distance between the jaw contacts, while the narrowest dimension of the beaver-tail configuration is significantly less than the distance between the jaw contacts. This enables the beaver-tail portion to enter rather deeply into the region between the jaw cooperating contacts before it is twisted into firm electrical engagement with these contacts.

The jaw assembly 18 of the present invention is shown as being located directly above the operating mechanism 14 (in some cases by a distance of more than 22 feet). The jaw assembly is comprised of a vertically aligned tubular member 19 having its upper end coupled to a T-connector 20, which in turn, is secured to an overhead wire, tube or other structure 21. The jaw assembly is suspended from vertically aligned tube 19 by means of a connector 22 which is welded or otherwise secured to the lower end of tube 19. The cooperating contacts of the jaw structure are located on opposite sides of connector 22 and are secured thereto by any suitable means. Only one contact, namely jaw contact 23, is shown in the figure for purposes of simplicity, it being understood that the remaining cooperating contact lies immediately behind and a spaced distance from contact 23. A pair of tubular metallic closed loop shield members 24 and 25 are secured to connector 22. Both FIGS. 1 and 2 show the brackets 24a and 25a employed to secure shields 24 and 25 to connector 22. It should be understood that similar connecting straps are provided for securing shield 25 to the opposite side of connector 22. The shields 24 and 25 act to significantly reduce dielectric stress concentration of the jaw structure components, some of which have rather sharp edges or contours, in cases when the switch is in the closed position or alternatively in those cases when the switch is in the open position and the jaw structure is energized (i.e. at an elevated voltage).

A cantilevered support structure 26 (shown in FIG. 1) which may be of relatively light weight extends outwardly in substantially the horizontal direction from assembly 14 and is secured thereto at its left hand end. This cantilevered structure is provided with a pair of shield members either welded or otherwise secured to the cantilevered structure. These shields greatly reduce the dielectric stress concentration which may occur in the region of sharp edges or contours along the blade beaver-tail portion in cases when the blade is in the substantially horizontal position, as shown in solid line in FIG. 1 and when the switch operating mechanism and hence the blade is energized (i.e. at an elevated voltage relative to the earth).

In FIG. 1 the operating mechanism 14 and hence the blade 15 is coupled to an external power source or load through conductor 29. In FIG. 2, the cantilevered member 26 performs the dual functions of supporting the shields 27 and 28 and electrically connecting the blade end of the disconnect switch to a source or a load. In the case where the blade portion of the disconnect switch is energized when in the open position and the conductor take-off utilizes the conductor 29, the blade end shield rings 27 and 28 are mounted upon a rigid cantilevered support (FIG. 1) as was previously described. In the case where the blade is energized when open and the conductor take-off 26 is utilized as both the conductor and shield support the blade and shield rings 27 and 28 are mounted directly upon conductor 26 (FIG. 2).

The disconnect switch jaw structure may be provided with an ice shield 30 positioned above the jaw structure 18 and secured to a connector 31 which, in turn, is secured near the upper end of tube 19. The function of the ice shield is to prevent the accumulation of rain, snow or sleet or other undesirable matter upon the jaw structure and thereby reduce the amount of ice loading which may develop upon the jaw structure and especially upon its contacts. The ice shield 30 may be positioned only a slight distance above the beaver-tail portion of the blade (when the blade is in the dotted line position 15) and thereby be most effective in reducing the amount of ice loading. In prior art structures which are provided with a large metallic ball or sphere at the end of the blade, such spheres add more than one foot to the length of the blade and their large surface areas subject them to rather appreciable ice loading making the operating effort required to move the blade into the closed or vertical position quite objectionable. In addition thereto, the ice shield must be located well above the top edge of the ball positioned at the extreme end of the blade thereby reducing the effectiveness of the ice shield in preventing ice loading or accumulation of other foreign matter upon the jaw contacts.

It can clearly be seen from the foregoing description that the present invention provides novel shielding means for vertical reach disconnect switches, especially those of large size and high voltage rating wherein dielectric stress concentration of energized switch components is significantly reduced in cases when the switch is in either the open or the closed position and wherein the operating forces to move the switch blade between the open and closed positions is significantly reduced as compared with conventional devices.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art.

Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

What is claimed is:

1. A vertical reach disconnect switch comprising:

a switch blade;

a jaw structure;

means for rotating said switch blade to move the free end of said switch blade from a substantially horizontal position toward a vertical position to engage said jaw structure which is positioned above said rotating means;

the extreme end of said blade being provided with a beaver-tail portion adapted to engage said jaw structure;

a support member extending from said rotating means generally in a horizontal position and being positioned immediately below said blade when said blade is in the horizontal position;

a pair of metallic conductive shield members arranged in substantially spaced parallel fashion and being secured to said support member so as to lie on opposite sides of the free end of said blade when in the horizontal position and thereby reduce dielectric stress concentration of the blade free end portion.

2. The switch of claim 1 further comprising a second pair of metallic conductive shield members arranged in substantially spaced parallel fashion and being secured to opposite sides of said jaw structure for reducing dielectric stress concentration of the jaw structure and of said blade free end portion when said blade is in the vertical position.

3. The switch of claim 2 further comprising a third pair of metallic conductive shield members arranged in substantially spaced parallel fashion and being secured to opposite sides of said rotating means for reducing dielectric stress concentration of the rotating means.

References Cited UNITED STATES PATENTS 3,009,995 11/1961 Turgeon.

ROBERT K. SCHAEFER, Primary Examiner H. I. HOHAUSER, Assistant Examiner US. Cl. X.R. 174-144; 3l7262 

